1. Field of the Invention
This invention relates to an improved structure for nonsynchronized positive clutches of the type comprising a first clutch member fixed for rotation, with a degree of rotational freedom, to a first rotatable device and selectively engagable with a second clutch member rotatable with a second rotatable device. The first clutch member is typically splined to a shaft for rotation therewith and axial movement relative thereto and is selectively axially movable relative to a gear carrying the second clutch member for selectively engaging and disengaging the positive clutch to selectively rotationally couple and decouple the gear to and from the shaft.
More particularly, the present invention relates to an axially engagable and disengagable nonsynchronized positive clutch structure wherein the number of interengagable clutch teeth carried by the clutch members is considerably greater (preferably at least fifty percent greater, more preferably at least one hundred percent greater) than the number of clutch teeth utilized with the corresponding nonsynchronized positive clutch structures of the prior art.
2. Description of the Prior Art
Nonsynchronized positive clutch systems for selectively rotationally coupling and decoupling a first rotatable device, such as a gear, to a second rotatable device, such as a shaft, are, of course, well known in the prior art. Change gear transmissions utilizing such positive clutches, without synchronizing mechanisms to minimize the cost, size and/or complexity thereof, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 2,951,395; 3,105,395; 3,335,616; 3,500,695; 3,799,002; 4,388,838; 4,754,665; 5,000,060 and 5,052,535, the disclosures of which are hereby incorporated by reference.
The clutch members of nonsynchronized positive clutch systems are, preferably, provided with clutch teeth having a leading edge structure which, during a clutch engagement, will tend to cause the clutch members to ratchet rather than engage if the relative rotational speeds thereof exceed a predetermined value. An example of such a clutch tooth structure may be seen by reference to U.S. Pat. No. 3,265,173, the disclosure of which is hereby incorporated by reference. As is known, for a given engagement force, the maximum allowable relative rotational speed at which the positive clutches will properly engage (i.e. sufficient clutch tooth penetration will occur) is a directly proportional function of the total effective backlash in the clutch system. The maximum allowable asynchronous conditions at which clutch engagement is allowed is selected in view of the most harsh clutch engagement which is acceptable.
While change gear transmissions utilizing the nonsynchronized positive clutch structures of the prior art, especially for heavy duty vehicles (MVMA Class 6 and larger), are very commercially successful, such transmissions and clutch structures are not totally satisfactory as the prior art clutches typically utilize a relatively small number of clutch teeth, typically 18 to 20 on the clutch members, which tends to result in the vehicle operator applying a larger force to cause engagement which will result in harsher and further out of synchronous clutch engagements than is desirable.
Certain prior art manually shifted nonsynchronized transmissions, such as Assignee of the present invention Eaton Corporation's Model T-11607 transmissions, have had one or more relatively larger diameter nonsynchronized positive clutches having a relatively large number of clutch teeth (30 clutch teeth per clutch member), however, no attempt has been made to maximize the number of clutch teeth utilized with such clutches.